[riscv64] Fix unreachable break

This is causing a warning on newer build configs (crrev.com/c/3117087)

Change-Id: I8cf7644861c27b9959283510163ecf8acdb6bdc8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3124174
Auto-Submit: Yahan Lu <yahan@iscas.ac.cn>
Commit-Queue: Ji Qiu <qiuji@iscas.ac.cn>
Reviewed-by: Ji Qiu <qiuji@iscas.ac.cn>
Cr-Commit-Position: refs/heads/main@{#76523}

src/codegen/riscv64/assembler-riscv64.cc

@@ -377,7 +377,7 @@ int Assembler::target_at(int pos, bool is_internal) {
       } else {
         return pos + imm13;
       }
-    } break;
+    }
     case JAL: {
       int32_t imm21 = JumpOffset(instr);
       if (imm21 == kEndOfJumpChain) {
@@ -386,7 +386,7 @@ int Assembler::target_at(int pos, bool is_internal) {
       } else {
         return pos + imm21;
       }
-    } break;
+    }
     case JALR: {
       int32_t imm12 = instr >> 20;
       if (imm12 == kEndOfJumpChain) {
@@ -395,7 +395,7 @@ int Assembler::target_at(int pos, bool is_internal) {
       } else {
         return pos + imm12;
       }
-    } break;
+    }
     case LUI: {
       Address pc = reinterpret_cast<Address>(buffer_start_ + pos);
       pc = target_address_at(pc);
@@ -409,7 +409,7 @@ int Assembler::target_at(int pos, bool is_internal) {
         DCHECK(pos > delta);
         return pos - delta;
       }
-    } break;
+    }
     case AUIPC: {
       Instr instr_auipc = instr;
       Instr instr_I = instr_at(pos + 4);
@@ -417,18 +417,18 @@ int Assembler::target_at(int pos, bool is_internal) {
       int32_t offset = BrachlongOffset(instr_auipc, instr_I);
       if (offset == kEndOfJumpChain) return kEndOfChain;
       return offset + pos;
-    } break;
+    }
     case RO_C_J: {
       int32_t offset = instruction->RvcImm11CJValue();
       if (offset == kEndOfJumpChain) return kEndOfChain;
       return offset + pos;
-    } break;
+    }
     case RO_C_BNEZ:
     case RO_C_BEQZ: {
       int32_t offset = instruction->RvcImm8BValue();
       if (offset == kEndOfJumpChain) return kEndOfChain;
       return pos + offset;
-    } break;
+    }
     default: {
       if (instr == kEndOfJumpChain) {
         return kEndOfChain;
@@ -437,7 +437,7 @@ int Assembler::target_at(int pos, bool is_internal) {
             ((instr & static_cast<int32_t>(kImm16Mask)) << 16) >> 14;
         return (imm18 + pos);
       }
-    } break;
+    }
   }
 }
 
@@ -2766,7 +2766,6 @@ int Assembler::RelocateInternalReference(RelocInfo::Mode rmode, Address pc,
     return 8;  // Number of instructions patched.
   } else {
     UNIMPLEMENTED();
-    return 1;
   }
 }
 

src/codegen/riscv64/macro-assembler-riscv64.cc

@@ -2452,7 +2452,6 @@ void TurboAssembler::CompareI(Register rd, Register rs, const Operand& rt,
       break;
     case cc_always:
       UNREACHABLE();
-      break;
     default:
       UNREACHABLE();
   }
@@ -3018,7 +3017,6 @@ bool TurboAssembler::BranchShortCheck(int32_t offset, Label* L, Condition cond,
     DCHECK_EQ(offset, 0);
     return BranchShortHelper(0, L, cond, rs, rt);
   }
-  return false;
 }
 
 void TurboAssembler::BranchShort(int32_t offset, Condition cond, Register rs,
@@ -3134,7 +3132,6 @@ bool TurboAssembler::BranchAndLinkShortCheck(int32_t offset, Label* L,
     DCHECK_EQ(offset, 0);
     return BranchAndLinkShortHelper(0, L, cond, rs, rt);
   }
-  return false;
 }
 
 void TurboAssembler::LoadFromConstantsTable(Register destination,

src/compiler/backend/riscv64/code-generator-riscv64.cc

@@ -106,7 +106,6 @@ class RiscvOperandConverter final : public InstructionOperandConverter {
             constant.ToDelayedStringConstant());
       case Constant::kRpoNumber:
         UNREACHABLE();  // TODO(titzer): RPO immediates
-        break;
     }
     UNREACHABLE();
   }
@@ -1919,7 +1918,6 @@ void AssembleBranchToLabels(CodeGenerator* gen, TurboAssembler* tasm,
         break;
       default:
         UNSUPPORTED_COND(instr->arch_opcode(), condition);
-        break;
     }
   } else if (instr->arch_opcode() == kRiscvMulOvf32) {
     // Overflow occurs if overflow register is not zero
@@ -1932,7 +1930,6 @@ void AssembleBranchToLabels(CodeGenerator* gen, TurboAssembler* tasm,
         break;
       default:
         UNSUPPORTED_COND(kRiscvMulOvf32, condition);
-        break;
     }
   } else if (instr->arch_opcode() == kRiscvCmp) {
     cc = FlagsConditionToConditionCmp(condition);
@@ -2597,7 +2594,6 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
         }
         case Constant::kRpoNumber:
           UNREACHABLE();  // TODO(titzer): loading RPO numbers
-          break;
       }
       if (destination->IsStackSlot()) __ Sd(dst, g.ToMemOperand(destination));
     } else if (src.type() == Constant::kFloat32) {

src/compiler/backend/riscv64/instruction-selector-riscv64.cc

@@ -563,7 +563,6 @@ void InstructionSelector::VisitStore(Node* node) {
         break;
 #else
         UNREACHABLE();
-        break;
 #endif
       case MachineRepresentation::kMapWord:            // Fall through.
       case MachineRepresentation::kNone:

src/diagnostics/riscv64/disasm-riscv64.cc

@@ -1882,7 +1882,7 @@ const char* NameConverter::NameOfXMMRegister(int reg) const {
 
 const char* NameConverter::NameOfByteCPURegister(int reg) const {
   UNREACHABLE();  // RISC-V does not have the concept of a byte register.
-  return "nobytereg";
+  //return "nobytereg";
 }
 
 const char* NameConverter::NameInCode(byte* addr) const {

src/execution/riscv64/simulator-riscv64.cc

@@ -172,7 +172,6 @@ bool RiscvDebugger::GetValue(const char* desc, int64_t* value) {
   } else {
     return SScanF(desc, "%" SCNu64, reinterpret_cast<uint64_t*>(value)) == 1;
   }
-  return false;
 }
 
 #define REG_INFO(name)                             \
@@ -1424,7 +1423,6 @@ void Simulator::SoftwareInterrupt() {
             break;
           default:
             UNREACHABLE();
-            break;
         }
       }
       switch (redirection->type()) {
@@ -1459,7 +1457,6 @@ void Simulator::SoftwareInterrupt() {
         }
         default:
           UNREACHABLE();
-          break;
       }
       if (::v8::internal::FLAG_trace_sim) {
         switch (redirection->type()) {
@@ -1473,7 +1470,6 @@ void Simulator::SoftwareInterrupt() {
             break;
           default:
             UNREACHABLE();
-            break;
         }
       }
     } else if (redirection->type() == ExternalReference::DIRECT_API_CALL) {